diff --git a/server/__tests__/converters.spec.js b/server/__tests__/converters.spec.js
index 6d6578f..508a03a 100644
--- a/server/__tests__/converters.spec.js
+++ b/server/__tests__/converters.spec.js
@@ -97,12 +97,12 @@ describe('buildArgs', () => {
 
   it('accepts jp2a RGB weight values', () => {
     expect(buildArgs('jp2a', { red: '0.5', green: '0.3', blue: '0.2' })).toEqual([
-      '--red', '0.5', '--green', '0.3', '--blue', '0.2',
+      '--red=0.5', '--green=0.3', '--blue=0.2',
     ])
   })
 
   it('accepts jp2a edge-threshold', () => {
-    expect(buildArgs('jp2a', { 'edge-threshold': '0.4' })).toEqual(['--edge-threshold', '0.4'])
+    expect(buildArgs('jp2a', { 'edge-threshold': '0.4' })).toEqual(['--edge-threshold=0.4'])
   })
 
   it('accepts valid img2txt format values', () => {
diff --git a/server/lib/converters.js b/server/lib/converters.js
index f5b5654..eec64b2 100644
--- a/server/lib/converters.js
+++ b/server/lib/converters.js
@@ -22,6 +22,8 @@ export const SCHEMAS = {
     format:            { type: 'value', valid: ['symbols', 'utf8'] },
   },
   jp2a: {
+    _argFormat: 'equals',
+    size:             { type: 'value' },
     width:            { type: 'value' },
     height:           { type: 'value' },
     chars:            { type: 'value' },
@@ -60,6 +62,7 @@ export function buildArgs(tool, flags) {
   const schema = SCHEMAS[tool]
   if (!schema) throw new Error(`Unknown tool: ${tool}`)
 
+  const equals = schema._argFormat === 'equals'
   const args = []
   for (const [key, value] of Object.entries(flags)) {
     const def = schema[key]
@@ -69,6 +72,8 @@ export function buildArgs(tool, flags) {
     }
     if (def.type === 'bool') {
       if (value) args.push(`--${key}`)
+    } else if (equals) {
+      args.push(`--${key}=${String(value)}`)
     } else {
       args.push(`--${key}`, String(value))
     }
@@ -87,7 +92,12 @@ export async function runChafa(imagePath, flags) {
 }
 
 export async function runJp2a(imagePath, flags) {
-  const args = buildArgs('jp2a', flags)
+  const { width, height, ...rest } = flags
+  const processed = { ...rest }
+  if (width && height) processed.size = `${width}x${height}`
+  else if (width) processed.size = `${width}x`
+  else if (height) processed.size = `x${height}`
+  const args = buildArgs('jp2a', processed)
   return execa('jp2a', [...args, imagePath], { timeout: TIMEOUT })
 }